# std::is_pointer

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< cpp‎ | types

Defined in header `<type_traits>` |  |
template< class T > struct is_pointer; |  | (since C++11)

`std::is_pointer` is a UnaryTypeTrait.

Checks whether `T` is a pointer to object or function (including pointer to void, but excluding pointer to member) or a cv-qualified version thereof. Provides the member constant `value` which is equal to true, if `T` is an object/function pointer type. Otherwise, `value` is equal to false.

If the program adds specializations for `std::is_pointer` or `std::is_pointer_v`, the behavior is undefined.

### Template parameters

T | - | a type to check

### Helper variable template

template< class T > constexpr bool is_pointer_v = is_pointer<T>::value; |  | (since C++17)

## Inherited from std::integral_constant

### Member constants

value [static] | true if `T` is a pointer type, false otherwise (public static member constant)

### Member functions

operator bool | converts the object to bool, returns value (public member function)
operator() (C++14) | returns value (public member function)

### Member types

Type | Definition
`value_type` | bool
`type` | std::integral_constant<bool, value>

### Possible implementation

    template<class T>
    struct is_pointer : std::false_type {};

    template<class T>
    struct is_pointer<T*> : std::true_type {};

    template<class T>
    struct is_pointer<T* const> : std::true_type {};

    template<class T>
    struct is_pointer<T* volatile> : std::true_type {};

    template<class T>
    struct is_pointer<T* const volatile> : std::true_type {};

### Example

Run this code

    #include <type_traits>

    int main()
    {
        struct A
        {
            int m;
            void f() {}
        };

        int A::*mem_data_ptr = &A::m;     // a pointer to member data
        void (A::*mem_fun_ptr)() = &A::f; // a pointer to member function

        static_assert(
               ! std::is_pointer<A>::value
            && ! std::is_pointer_v<A>    // same thing as above, but in C++17!
            && ! std::is_pointer<A>()    // same as above, using inherited operator bool
            && ! std::is_pointer<A>{}    // ditto
            && ! std::is_pointer<A>()()  // same as above, using inherited operator()
            && ! std::is_pointer<A>{}()  // ditto
            &&   std::is_pointer_v<A*>
            &&   std::is_pointer_v<A const* volatile>
            && ! std::is_pointer_v<A&>
            && ! std::is_pointer_v<decltype(mem_data_ptr)>
            && ! std::is_pointer_v<decltype(mem_fun_ptr)>
            &&   std::is_pointer_v<void*>
            && ! std::is_pointer_v<int>
            &&   std::is_pointer_v<int*>
            &&   std::is_pointer_v<int**>
            && ! std::is_pointer_v<int[10]>
            && ! std::is_pointer_v<std::nullptr_t>
            &&   std::is_pointer_v<void (*)()>
        );
    }

### See also

is_member_pointer (C++11) | checks if a type is a pointer to a non-static member function or object (class template)
is_member_object_pointer (C++11) | checks if a type is a non-static member object pointer (class template)
is_member_function_pointer (C++11) | checks if a type is a non-static member function pointer (class template)
is_array (C++11) | checks if a type is an array type (class template)
is_scalar (C++11) | checks if a type is a scalar type (class template)

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